Fairfax Media Network

Agriculture Weather


Southern Oscillation Index

  • location
  • Aus

The Southern Oscillation Index (SOI) is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

A strongly and consistently positive SOI pattern (e.g. consistently above about +6 over a two month period) is related to a high probability of above the long-term average (median) rainfall for many areas of Australia, especially areas of eastern Australia (including northern Tasmania) - La Niņa.

Conversely, a 'deep' and consistently negative SOI pattern (less than about minus 6 over a two month period, with little change over that period) is related to a high probability of below median rainfall for many areas of Australia at certain times of the year - El Niņo.

However, it is important to remember that the pattern of relationship between SOI and rainfall (and temperature) can vary depending on the particular season and region. Additionally, the change in SOI over a specified period can be as important in understanding relationships between SOI and rainfall as is the absolute value in SOI.

Southern Oscillation Index

SOI

Nino3.4 Index

Nino3.4
Display Your Local Weather

Weather News

VIC missing out on June's rain

15:26 EST

The start of winter was a dry one for much of Victoria.

Boisdale community shares information to prepare for Avon River flooding

15:00 EST

Keeping a community together, and planning for flooding can sometimes be tricker than an initial emergency response.

Falling rain and rising prices bring smiles to drought-stricken Charleville

14:20 EST

Rain and high cattle prices have brought a sense of optimism to the drought stricken Queensland community of Charleville, but locals warn farmers are still struggling as the dry continues.